Process control systems, like those used in chemical, petroleum or other processes, typically include one or more process controllers and input/output (I/O) devices communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital or combined analog/digital buses. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure and flow rate sensors), perform functions within the process such as opening or closing valves and measuring process parameters. The process controllers receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, use this information to implement a control routine, and then generate control signals that are sent over the buses or other communication lines to the field devices to control the operation of the process. In this manner, the process controllers may execute and coordinate control strategies using the field devices via the busses and/or other communication links communicatively coupling the field devices.
Process control systems are often configured to perform processes in accordance with batch recipes to produce products. Product designers or engineers prepare recipes during a design time and store the recipes to be subsequently used a plurality of times by a process control system. A recipe typically includes a combination of unit procedures, operations, and phases, all of which include instructions to control process equipment (e.g., tanks, vats, mixers, boilers, evaporators, pumps, valves, etc.) to transfer, mix, etc. ingredients in a process control system to generate a product.
In a typical scenario, a process control system executes the recipe from start to finish to produce a desired product. However, in some cases, a need arises to depart from the normal process flow of a recipe due to, for example, an error in an ingredient, a need to refine a product, an external or environmental factor (e.g., temperature, humidity, etc.) that adversely affects certain operations, etc. Recipes are often intended to execute from start to finish without interruption or modification of the recipe. Thus, there are currently no easy methods by which a recipe can be modified once its execution has begun. If an error has occurred in a process during execution of a recipe for whatever reason or if modification of the recipe is desired after execution has begun, costly ingredients that have been partially processed may have to be scrapped to redesign the recipe during a design time and followed by a restart of the recipe. One traditional method of modifying a recipe during its execution requires an experienced operator or group of operators working together to manually shutdown certain process steps of the recipe, remove or circumvent unwanted process steps from the recipe, and insert desired process steps while ensuring that none of the modifications violate company standard process flow rules and/or industry standard process flow rules. Such a manual process is tedious, costly, and time consuming and prone to error because it requires significant expertise on the part of operator(s) to ensure that product quality is not adversely affected and/or that safe operating conditions are maintained.